July i6, 1917 Movement and Distribution of Moisture in Soil 141 



figure shows that as the initial percentage of water in the wet soil de- 

 creased, the length of time of the rapid moisture movement also decreased. 

 It was also found that the water moved downward into the soil faster 

 than it moved upward and that an approach to an equilibrium is reached 

 sooner by the downward movement. The moisture moved down 

 farther than up during these 46 days. From this experiment it is seen 

 that loam soil with as high as 18.5 per cent of moisture gives up water 

 to air-dry soil at a very slow rate, especially after the fiirst week. In all 

 cases the rapid movement into the drier soil had practically ceased by 

 the end of the first week. 



EFFECT OF GRAVITY 



With Varying Initial Percentages op Moisture in the Source op Supply 



The data for the first part of this experiment on the effect of gravity 

 on the movement of soil moisture were taken from the above experiment. 



Percent mofsture 

 offer capillary moyement 



J£. 



Average percent y ryafer in source of 3upp/(/ 



^6 e.i ez ^/ // IS /i /J? /fi f 6 



^Moisture in source of supply 

 ^Downward moi^emcnt 

 mUpward movement 



Fig. 22. — Diagram showing the average final distribution of moisture which moved upward and down 

 ward by capillarity through Greenville loam, air-dried, with a varying moisture content in the soiu-ce 

 of supply. 



Figure 22 shows how the average moisture content in each of the 

 cylinders that originally had 2.12 per cent of moisture was affected by 

 gravity where different quantities of water in the soil were used as 

 sources of supply. That gravity plays relatively little part in the 

 distribution of moisture in dry soils where the sources of water are 

 moderately moist soils is the conclusion from this figure. There was 

 slightly more moisture in the soil supplied by upward movement where 

 the initial percentage of water in the soil supplying moisture was rather 

 low, but the reverse was true elsewhere. "^ 



